Limb-shortening deformities and bone segmental defects remain among the most difficult challenges faced by patients and orthopaedists. Traditional techniques to correct these problems rely primarily on transverse pins or wires, which are subject to pain, scars, contractions, and risk of infection. The Phase I research demonstrated the feasibility of a new method for bone lengthening/transport, based on distraction osteogenesis, and using intramedullary rod fixation and a single, longitudinal traction cable actuator. The specific aim of the work is develop a completely implantable actuator to drive cable motion, thus eliminating all percutaneous penetration of wires, minimizing patient intervention, and making the need for rod exchange unlikely. In Phase I, six engineering prototype actuators were designed, built and successfully bench-tested with varying distraction forces to 1,200 N. In Phase II, the final-form distraction actuator -high-powered, self-contained and remotely controlled - will be developed, tested and combined with a largely existing suite of intramedullary nails and associated implant hardware. The successful Phase II development of a capable, cost-effective actuator, occupying a volume of 160 cc or less and weighing 200 g or less, will set the stage for the Phase III commercial development of a fully implantable bone lengthening and transport system.